This invention relates to novel thermoplastic, elastomeric polymeric materials formed by grafting short chain 6-nylons or 12-nylons onto rubbery trunk polymers.
Most elastomers can be molded or extruded into various shapes. The fabricated articles may include, for example, automotive trim, bumper inserts, and hoses. Usually, these elastomers have low strength and must be crosslinked after being shaped into the desired article. The curing step usually requires compounding with suitable agents such as sulfur, peroxides, and the like, before shaping. The thermal sensitivity of the compounded curable compositions may cause premature curing ("scorch") and loss of plasticity. Radiation cures, which do not involve compounding, are generally only effective with thin cross sections; degradation may compete with crosslinking. Furthermore, cured scrap and cured shaped articles which have defects are not conveniently reused. Accordingly, it would be desirable to have thermoplastic elastomers which require no cure and can be shaped repeatedly by heating to give articles having satisfactory strength and dimensional stability at the temperatures prevailing during their use. Blends and grafts of polymers are known in the art to give thermoplastic products which often have improved properties.
Tutorskii et al., Journal Polymer Sc. 61, 97-106 (1962) reports grafting of .epsilon.-caprolactam onto carboxylated butadiene-styrene rubbers by heating the rubber and the lactam above 200.degree. C. in the presence of boron trifluoride.
Chapman et al., Journal Polymer Sc. 34, 319-335 (1959) report the polymerization of .epsilon.-caprolactam at elevated temperatures in the presence of a copolymer of styrene with methyl acrylate, acrylic acid, or maleic anhydride. Gelling was observed in several instances, especially with styrene/maleic anhydride copolymers.
U.S. Pat. No. 3,484,403 describes certain hot melt adhesive and coating compositions based on blends of polyamides with grafts of unsaturated dicarboxylic acids or their anhydrides on polyolefin backbone.
U.S. Pat. No. 3,261,885 discloses block-graft copolymers obtained by subjecting to high shear conditions at 50.degree.-350.degree. C. a mixture of C.sub.2 -C.sub.4 olefin or styrene copolymers with up to 50 weight percent of another unsaturated monomer with various synthetic linear polyamides in the presence of free radical generators.
Yurkevich et al., Khimicheskie Volokna No. 3, 11-13 (1971) (1972, Consultants Bureau's English translation) reports experiments with graft copolymers of polycaproamide (6-nylon) with vinyl monomers, such as acrylonitrile, styrene, acrylic acid, and various acrylic esters. While no experimental details are given, it appears that the vinyl monomers were grafted onto polycaproamide. The resulting products were examined for possible use in melt spinning of fibers.
U.S. Pat. No. 3,676,400 discloses melt extrusion of mixtures of certain amino-terminated polyamides having molecular weights of at least 2000, and preferably 10,000-40,000, with copolymers of 2-monoolefins and unsaturated mono- or dicarboxylic acids.
None of the prior art suggests grafting of amino-terminated 6- or 12-nylons on rubbery materials to produce thermoplastic elastomers of improved mechanical properties.